Control system



J1me 1936- R. s. ELBERTY, JR 2,045,331

CONTROL SYSTEM Filed Aug. 13, 1931 WINESSES: INVENTOR I Faber) SE/ber/j'y, Jr: 2 W

' ATT( )RNE Y Patented June 23, 1936 UNITED STATES PATENT OFFICE CONTROL SYSTEM Ohio Application August 13, 1931, Serial No. 556,819

15 Claims.

My invention relates generally to control systems and particularly to control systems for drying machines, such as drying tumblers for laundries and the like.

As is apparent, the efficiency and capacity of a drying machine may be materially increased by providing a control system that functions to discontinue the drying process when the moisture of the material is reduced to a predetermined value.

0 In this manner, the material is not kept in the drying machine for any longer period of time than is necessary.

In this connection, it has been determined by tests that the electrical conductivity of cloth varies from substantially zero, when dry, to a relatively high value at 50% of moisture saturation and above. To utilize this change in conductivity for control purposes is an object of my invention.

It is also an object of my invention to provide a control system of the class indicated that shall be simple and reliable and be readily and economically manufactured and installed.

Another object of my invention is to provide for extracting moisture from damp material and for discontinuing such extracting process when the moisture content of the material is reduced to a predetermined value.

A further object of my invention is to provide 9 for controlling the operations of a drying machine in accordance with the moisture content of the material being dried.

A more specific object of my invention is to provide for discontinuing the operations of a drying machine when the electrical conductivity of the material attains a predetermined value.

Other objects of my invention will hereinafter become apparent.

For a fuller understanding of the nature and the objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Figfi're 1 is a diagrammatic view of a control system constructed in accordance with my invention and shown in relation to a drying tumbler,

and

Fig. 2 is a view, in vertical cross-section, taken along the line IIII of Fig. 1 and showing partlcularly a door-operated switch and the manner in which the current conducting bars are disposed within the rotatively-mounted receptacle.

Referring now to the drawing, reference character I 0 represents an enclosure or housing for a drying machine, such as a drying tumbler for laundries and the like. A cylinder I! having perforations I4 is rotatively mounted within the housing and constitutes a receptacle in which the material to be dried is disposed during the drying process.

As illustrated, a motor 20 of any suitable type is provided to rotate the cylinder I2 by means of gear wheels 22 and 24. As is the usual practice in drying machines, a current of hot air is passed through the cylinder l2 and brought into intimate contact with the material in order to reduce the drying time to a minimum. For this purpose,

a fan l6 mounted on top of the housing I II is provided. A motor I! of any suitable type, preferably one that may operate in parallel with the 15 motor 20, is provided to rotate the fan l6 during the drying process. The motors l1 and 20 are simultaneously energized from a source of three-phase power comprising the supply conductors 45, 46 and 41 when the switch I0 is energized.

A cold cathode gaseous electric discharge device 35 of a familiar type that is disposed to be influenced by the moisture content of the material being dried, is connected in circuit with the relay 60. When the moisture content of the material being dried is above a predetermined amount, the electric discharge device 35 operates a relay 60, which, in turn, establishes a circuit for closing the switch 10. Conversely, when the moisture content of the material being dried is reduced to a predetermined amount by the drying process, the electric discharge device 35 ceases to operate, thereby deenergizing the motors 35 I1 and 20.

During the drying process, the motor I I operates the fan IE to induce a draft of heated air through the cylinder l2 in order to hasten the drying process. The air upon entering the hous- 0 ing I 0 through an opening 19 provided in the bottom part thereof passes over the heating elements l8, such as steam pipes.

Also during the drying process, the motor 20 slowly rotates the cylinder H! in order to provide 45 for uniformly drying the material and also for lessening the drying period. As is the usual practice, a plurality of inwardly projecting longitudinal ribs 26, as illustrated, are disposed within the cylinder to stir or to agitate the material as 50 the cylinder rotates.

However, in the preferred embodiment of my invention, I provide for constructing each rib of a current-conducting bar 28 insulated from the periphery of the cylinder by means of an insulating bar" of Micarta or any other suitable insulating material. In this manner, the ribs may be utilized as part of the control circuit as well as means for stirring the material while the cylinder rotates.

Preferably, as shown, the conducting bars 28 are connected at one end by means of a ring 30 which in turn is electrically connected to the control electrode 36 of the electric discharge device 35, by means of a slip ring 32, insulated from the cylinder, and conductors 31 and 3B.

The anode 40 and the cathode 411, which will be referred to as the principal electrodes of the electric discharge device are connected across one phase of the three-phase supply source. This circuit extends from the supply conductor 45 through conductors 49 and 50, the principal electrodes 40 and 4i, conductor 5i, a manually-operated switch 52, conductor 53, the contact members of the door-operated switch 6! (see Fig. 2), conductor 54, the magnetizing windings of relay 60, and conductor to the supply conductor 46.

The principal electrode at is also connected in circuit with the cylinder l2 by means of a slip ring 43 that is electrically connected to the cylinder, and a conductor 44.

Consequently, the voltage between the control electrode 36 and the principal electrode 40 varies in accordance with the electrical conductivity of the material that is connecting the bars 28 to the cylinder i2. If the conductivity is high, as it will be when the material is very damp, the voltage between the control electrode 36 and the principal electrode til will likewise be high. At the same time, since the voltage between the principal electrodes 49 and M is substantially constant and equal to the voltage across the supply conductors, the voltage between the control electrode 36 and the principal electrode 48 increases. Therefore, when the voltage between the control electrode 36 and the principal electrode 40 decreases to a predetermined value, as determined by the moisture content of the material, the voltage between the control electrode 36 and the principal electrode 56 correspondingly increases to a predetermined value and causes the electric discharge device to operate.

The operation of the electric discharge device 35 permits current to flow freely between the principal electrodes 4|! and 4H and thereby energizes the relay 60. Accordingly, the closing of the contact members of the relay 6U establishes acircuit for energizing the magnetizing winding of switch 10. In this manner the motors H and 20 are energized from the supply source through the closing of the contact members of the switch 10. At the same time that the switch 10 is closed, a potential is established across a visible signal 15, such as a lamp. This is to indicate to the attendant that the motors are energized.

As hereinbefore explained, when the electricdischarge device 35 is operating, the motor I! drives the fan I6 for inducing a draft of heated air through the cylinder l2 for hastening the drying process. Likewise, the motor 20 rotates the cylinder in which the clothes are disposed in order to produce a. churning action to provide uniform drying. The motors continue to operate until the drying process has reduced the electrical conductivity of the material to a predetermined value, or in other words, until the moisture content of the material is reduced to a predetermined value.

As the moisture content of the material gradually decreases, the voltage between the control electrode 38 and the principal electrode 40 gradually increases and, correspondingly, the voltage between thecontrol electrode and the principal electrode 4| gradually decreases. When the voltage between the control electrode 36 and the 5 principal electrode 4| decreases to a predetermined value, the electric discharge device ceases operating, thereby deenergizing the relay 60 and the motors l1 and 20. The opening of the switch 10 likewise deenergizes the signal 15, which in-.? dicates to the attendant that the drying process has ceased.

An adjustable impedance device 16, which may be a resistor, a capacitor, or a reactor, or a combination of these, but which is preferably a resistor, is connected across the control electrode 36 and the principal electrode 4 I. As is apparent, the voltage between the control electrode and principal electrode may be varied by changing the value of the impedance of the device 16. Therefore, by varying the effect of the impedance device 16, the electric discharge device 35 may be caused to operate in accordance with any predetermined value of the moisture content of the material being dried.

Although I have preferably shown a cold cathode gaseous electric discharge device in the embodiment of my invention because of its desirable operating characteristics, I do not limit myself to such device, since other electric discharge devices, such, for example, as a grid controlled mercury vapor tube, a vacuum tube, or a hot cathode gaseous electric discharge device may be utilized.

In the interest of safety and also as a matter 35 of convenience for the attendant a door-operated switch 6! is provided to disrupt the control circuit through actuating coil of relay 60 when the door It is open (see Fig. 2). As is apparent, upon the opening of the door, the illustrated spring biases the contact members to opencircuit position.

I have thus shown and described a control system that provides for controlling the operations of a drying machine in accordance with the moisture content of the material being dried.

Since certain changes may be made in the above-described construction and since different embodiments of my invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A machine for drying material comprising, in combination, means for extracting moisture from said material, an electric discharge device disposed to be aifected by the moisture content of said material, and means responsive to the 60 condition of the electric discharge device for discontinuing the action of said extracting means.

2. A machine for drying material comprising, in combination, means including means for producing a draft of air for extracting moisture from said material, an electric discharge device disposed to be affected by the moisture content of said material, and means responsive to the condition of the electric discharge device for discontinuing the action of said extracting means.

3. A machine for drying material comprising, in combination, a receptacle for containing said material, means for establishing a draft of air to said material for drying said material, an electric discharge device disposed to be affected by the moisture content of said material, and.

means responsive to the condition of said electric discharge device for controlling the operation of said draft-establishing means.

4. A machine for drying material comprising in combination, a receptacle for containing said material, a fan, an electric motor for driving said fan to establish a draft of air to said material for drying said material, an electric discharge device disposed to be affected by the moisture content of said material, and means responsive to the condition of said electric discharge device for controlling said motor.

5. In a machine for drying material the combination of a receptacle for containing said ma,- terial, current-conducting means insulated from the receptacle and disposed to make contact with said material, an electric discharge device, a source of electrical energy and means including said receptacle and said current-conducting means for connecting said electric discharge device in circuit with said source of electrical energy.

6. A machine for drying material comprising, in combination, containing means for said material, current-conducting means insulated from said containing means and disposed to make contact with said material, means for establishing a draft of air in contact with said material, an electric discharge device connected in circuit with said containing means and said current-conducting means and disposed to be influenced by the moisture content of said material, and means responsive to the condition of the electric discharge device for controlling the draft-establishing means.

'1. A machine for drying material comprising, in combination, a rotatively mounted receptacle for containing said material, means for rotating the receptacle, current-conducting means insulated from said receptacle and disposed to make contact with said material, a fan for establishing a draft of air, means for driving said fan, an electric discharge device connected in circuit with said receptacle and said current-conducting means and disposed to be influenced by the moisture content of said material, and means responsive to the condition of said electric discharge device for controlling said means for rotating said receptacle and said means for driving said fan.

8. A machine for drying material comprising, in combination, a rotatively mounted receptacle for containing said material, a motor for rotating said receptacle, current-conducting means insulated from said receptacle and disposed to make contact with said material, a motor-driven fan for establishing a draft of air, means for energizing said motors, an electric discharge device connected in circuit with said receptacle and said current-conducting means and disposed to bc influenced by the moisture content of said material, and means responsive to the condition of said electric discharge device for deenergizing the motors.

9. A machine for drying material comprising, in combination, a receptacle for containing said material, means for operating said receptacle, means for establishing a draft of air to said material for drying said material, an electric discharge device disposed to be affected by the moisture content of said material, and means responsive to the operating condition of said electric discharge device for controlling the operations of said means for operating the receptacle and said draft establishing means, respectively.

10. A machine for drying material, in combination, a receptacle for containing said material, receptacle operating means, a fan, an electric motor for driving said fan to establish a draft of air to said material for drying said material, an electric discharge device connected to be affected by the moisture content of said material, and means responsive to the condition of said electric discharge device for controlling the receptacle operating means and the said motor, respectively.

11. In a machinefor drying material, moisture extracting means for drying said material, means for passing a current of electricity through said material, and means actuated when the flow of said current through said material is reduced below a predetermined value due to increase in resistance of said material to the flow of said current because of the extraction of moisture therefrom to discontinue the action of said moisture extracting means.

12. A machine for treating material comprising, in combination, means for supporting the material to be treated, means for extracting moisture from said material, electrical means arranged in circuit with said material so as to be affected by moisture content of said material, and means responsive to the condition of said electrical means for discontinuing action of said extracting means.

13. A machine for treating material containing moisture and having different electrical characteristics with different moisture contents, in combination, means for producing a draft of gaseous fluid for extracting moisture from said material, means for heating the gaseous fluid, means for passing an electric current through said material, and means actuated when the flow of said current through said material is varied a predetermined value due to the change in electrical characteristics of the material by reason of the change in moisture content, to discontinue the action of said means for producing a draft of gaseous fluid.

14. A machine for drying material comprising, in combination, a support for the material, current-conducting means insulated from said support and including means adapted to make contact with said material, means for establishing a draft of gaseous fluid in contact with said material to extract moisture therefrom, electrical means connected in circuit relation with said support and said current-conducting means and thus adapted to be influenced by the moisture content of the said material, and means responsive to the electrical condition of said electrical means for controlling the draft-establishing means.

15. A machine for drying material comprising, in combination, a rotatively mounted container for the material, means for rotating the container, current-conducting means insulated from said receptacle and adapted to make contact with said material, a fan for producing a draft of gaseous fluid to the material, means for driving the fan, electrical means interconnected with the container and the current-conducting means and adapted to be influenced by the moisture content of said material, and means, responsive to the condition of said electrical means, adapted to control the means for rotating said container and for driving said fan.

ROBERT S. ELBERTY, Jl. 

